Liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS) are analytical chemistry techniques that combine the physical separation capabilities of high performance liquid chromatography (or HPLC) with the mass analysis capabilities of mass spectrometry (MS). These systems are popular in chemical analysis because the individual capabilities of each technique are enhanced synergistically. While liquid chromatography separates mixtures with multiple components, mass spectrometry provides structural identity of the individual components with high molecular specificity and detection sensitivity.
In recent years, liquid chromatography tandem mass spectrometry (LC-MS/MS) has emerged as an innovative analytical technology applicable to some analyses in the endocrinology laboratory. In tandem MS (MS/MS) two quadrupole mass filters are combined and target analyte molecules from the first quadrupole are submitted to a controlled fragmentation in a collision cell. The entirety of ions is transferred into the first quadrupole mass filter. Here, the mass-to-charge ratio (m/z) of the intact ionized target analyte is selected, and all other ion species are filtered out. The selected ions sharing identical m/z are continuously transferred into the collision cell. Ions selected by the first quadrupole fragment into characteristic product ions. For various analytes, several characteristic, thermodynamically favored product ions are generated. These fragment ions are guided to the second quadrupole. The radiofrequency settings of the second analytical quadrupole are adjusted in a way that only one selected fragment ion will pass, while all other fragment ion species are filtered out. Thus, one defined “daughter ion” from one defined “parent ion” finally reaches an ion detector, and can then be identified and/or quantified.
Many medical procedures require tests to be performed with a sample of a patient's fluid. The ability to rapidly and accurately detect a wide range of analytes present in a bodily fluid is often critical for diagnosis, prognosis, and treatment of diseases, or for determining specific drugs that may be present in a patient's system.
Traditionally, detecting a range of analytes present in a bodily fluid such as blood has been performed in laboratories by trained technicians who take blood via venipuncture or using smaller blood samples such as by a finger stick. Performing such assays using LC-MS or LC-MS/MS can be time-consuming and costly. Running dozens or even hundreds of such tests to determine the presence (or absence) and/or quantity of various analytes characteristically requires a relatively large volume of blood. With conventional techniques, it is difficult to simultaneously test for a relatively large number of analytes. Consequently, each test requires a certain quantity of blood. The greater number of tests that are required, the greater the volume of blood that is needed from the patient.
Although several point of care testing devices are available, the majority of are adapted to detect a single analyte, or one type of analytes for a single indication, Examples of such point of care devices are tests for glucose, serum cholesterol, pregnancy, ovulation, etc.
Thus, there remains a need for alternative testing methods that are capable of detecting a wider range and/or greater number of analytes from biological samples such as dried blood, urine and/or other biological samples. A desirable system would allow quantitative and qualitative measurements of analytes in a more cost effective and timely manner.